Ar Ra’d Ayah 17

أَنزَلَ مِنَ ٱلسَّمَآءِ مَآءً فَسَالَتْ أَوْدِيَةُۢ بِقَدَرِهَا فَٱحْتَمَلَ ٱلسَّيْلُ زَبَدًا رَّابِيًا‌ۚ وَمِمَّا يُوقِدُونَ عَلَيْهِ فِى ٱلنَّارِ ٱبْتِغَآءَ حِلْيَةٍ أَوْ مَتَـٰعٍ زَبَدٌ مِّثْلُهُۥ‌ۚ كَذَٲلِكَ يَضْرِبُ ٱللَّهُ ٱلْحَقَّ وَٱلْبَـٰطِلَ‌ۚ فَأَمَّا ٱلزَّبَدُ فَيَذْهَبُ جُفَآءً‌ۖ وَأَمَّا مَا يَنفَعُ ٱلنَّاسَ فَيَمْكُثُ فِى ٱلْأَرْضِ‌ۚ كَذَٲلِكَ يَضْرِبُ ٱللَّهُ ٱلْأَمْثَالَ ١٧ He sends down rain from the sky, causing the valleys to flow, each according to its capacity. The currents then carry along rising foam, similar to the slag produced from metal that people melt in the fire for ornaments or tools. This is how Allah compares truth to falsehood. The ?worthless? residue is then cast away, but what benefits people remains on the earth. This is how Allah sets forth parables.